Bunsen devised methods for determining the _solubility of gases_ in liquids, for ascertaining the _specific gravity of gases_, their _rates of diffusion_, and of combination or _inflammation_. In 1841 he invented the _carbon-zinc battery_, and applied it to the electrolytic production of metals, notably of _magnesium_, the properties of which he first accurately described. In 1844 he contrived the _grease-spot photo-meter_, which was long in general use for ascertaining the photometric value of illuminating gas. His methods of ascertaining _the specific heats of solids and liquids_ were simple, ingenious, and accurate. In 1855–1863 he carried out, in conjunction with Roscoe, a long series of investigations on the _chemical action of light_. In 1859, in association with Kirchhoff, he devised the first methods of _spectrum analysis_, and explained the origin and significance of the Fraunhofer lines in the solar spectrum, thus laying the foundations of solar and stellar chemistry. The application of the _spectroscope_ to analytical chemistry almost immediately resulted in his discovery of _cæsium_ and _rubidium_. Bunsen worked on problems of _chemical geology_, and made a long series of analyses of _volcanic products_. With Schischkoff, he examined, in 1857, the products of fired gunpowder. He effected many improvements in analytical chemistry; devised the _iodiometric method_ of volumetric analysis, and systematised the processes of _water analysis_. Lastly, he invented the _gas-burner_—a piece of apparatus with which his name is inseparably associated, and which has been of inestimable service to operative chemistry and in the arts. Bunsen was no theorist, and purely speculative questions had little or no interest for him. At the same time he was a great teacher, and made the chemical school of Heidelberg no less famous than the schools of Giessen and Göttingen. * * * * *